Dec, 1921] PATON POLLEN AND POLLEN ENZYMES 499 



4. Washing the pollen before use was tried with corn, ragweed, and 

 Easter lily. I gram of unground pollen was shaken vigorously with 300 cc. 

 of distilled water in a liter cylinder, and then filtered into a sterile flask 

 through a sterilized Buchner funnel and filter paper, and washed four times 

 with sterile distilled water. Plates were poured from the last washing, 

 dilution 1 : 100. Some plates were sterile and others from the same filtrate 

 had from I to 19 colonies. The washed pollen when diluted and tested 

 showed a similar lack of constancy, so that there seems to be no gain in 

 washing, and this method may cause loss of enzymes. 



Repetition with dock pollen failed to show that it always had a higher 

 count. There was probably some initial contamination in preparing the 

 extract. 



Summary 



Although it has been assumed that pollen tubes digest their way through 

 the style, there is little experimental evidence as to the exact nature of this 

 enzyme action. Histological examination shows that in most instances 

 pollen tubes make their way between the walls of adjacent cells rather than 

 penetrating them. We should expect therefore to find most frequently not 

 a cytase- or cellulose-digesting enzyme, but rather a pectinase capable of 

 digesting the pectin of the inner lamella. This has been proved in the 

 writer's experiments to be the case. 



Eighteen species of pollen have been used; these have been tested for 

 thirteen kinds of enzymes. So far amylase, invertase, catalase, reductase, 

 and pectinase have been found in all. Pepsin, trypsin, erepsin, and lipase 

 have been demonstrated in some and not in others. Cytase was doubtfully 

 identified in six of the eighteen. Tyrosinase and laccase have not been 

 found in any, and zymase was found only in Siberian crab apple pollen. 



BIBLIOGRAPHY 



Adams, J. 1916. On the germination of the pollen grains of apple and other fruit trees. 



Bot. Gaz. 61: 131-147. 

 Allen, C. E. 1901. On the origin and nature of the inner lamella. Bot. Gaz. 32: 1-34. 

 Amici, G. B. 1830. Note sur la mode d'action du pollen sur le stigmate. Ann. Sci. Nat. 



21:329-332. 

 Biourge, P. 1892. Recherches morphologiques et chimiques sur les graines de pollen. 



La Cellule 8: 47-76. 

 Bower, F. O. 1919. Botany of the living plant. London. 

 Braconnot, H. 1829. Recherches chimiques sur le pollen du Typha latifolia. Ann. Chim. 



Phys. 42: 91-105. 

 Church, A. H. 1875. Some contributions to plant chemistry. Jour. Bot. 13: 169. 

 Coulter, J. M. 1910. Morphology of the gymnosperms. Chicago. 



, and Chamberlain, C. J. 1903. Morphology of the angiosperms. New York. 



Crabill, C. H., and Reed, H. S. 1915. Convenient methods for demonstrating the 



biochemical activity of micro-organisms, with special reference to the production 



and activity of enzymes. Paper no. 29, Lab. Plant Path. Bact., Ya. Agr. Exp. Sta. 



